1. Field of the Invention
This invention relates to a novel receptor protein recognizing a specific cytokine, more particularly, to a novel protein composing interleukin-18 receptor (hereinafter abbreviated as xe2x80x9cIL-18Rxe2x80x9d) or IL-18R protein, as well as to a monoclonal antibody specific to the IL-18R protein.
2. Description of the Prior Art
Interleukin-18 (hereinafter abbreviated as xe2x80x9cIL-18) is a type of cytokine or substance which mediates signal transduction in immune system. As seen in Japanese Patent Kokai Nos.27,189/96 and 193,098/96 and Haruki Okamura et al., Nature, Vol.378, No.6,552, pp.88-91 (1995), IL-18 was provisionally designated as xe2x80x9cinterferon-gamma inducing factorxe2x80x9d immediately after its discovery: This designation was changed later into xe2x80x9cIL-18xe2x80x9d in accordance with the proposal in Shimpei Ushio et al., The Journal of Immunology, Vol.156, pp.4,274-4,279 (1996). IL-18 in mature form consists of 157 amino acids and possesses properties of inducing in immunocompetent cells the production of interferon-gamma (hereinafter abbreviated as xe2x80x9cIFN-xcex3xe2x80x9d) which is known as useful biologically-active protein, as well as of inducing and enhancing the generation and cytotoxicity of killer cells. Energetic studies are now in progress to develop and realize various uses of IL-18 in pharmaceuticals such as antiviral, antimicrobial, antitumor and anti-immunopathic agents which have been in great expectation because of these properties of IL-18.
As described above, in nature, cytokines including IL-18 are produced and secreted as substances responsible for signal transduction in immune system. Therefore, excessive amounts of cytokines may disturb the equilibria in immune system when they are produced or administered in the body of mammals. The surface of usual mammalian cells may bear certain sites or xe2x80x9creceptorsxe2x80x9d which are responsible for recognition of cytokines: Secreted cytokines transduce no signal in cells till they are bound to the receptors. In normal immune system, there would be definite equilibria between respective cytokines and their receptors. Thus, in this field, with the purpose of developing and realizing IL-18 as pharmaceuticals, in addition to the clarification of physiological activities of IL-18, an expedited establishment of mass production and characterization of IL-18R protein have been in great expectation.
In view of the foregoing, the first object of this invention is to provide a receptor which recognizes IL-18.
The second object of this invention is to provide uses of the receptor as pharmaceuticals.
The third object of this invention is to provide a monoclonal antibody being reactive with the receptor.
The fourth object of this invention is to provide a hybridoma which is producible of the monoclonal antibody.
The fifth object of this invention is to provide a process to prepare the monoclonal antibody.
The sixth object of this invention is to provide a method to purify a receptor which recognize IL-18 using the monoclonal antibody.
The seventh object of this invention is to provide a method to detect a receptor which recognize IL-18 using the monoclonal antibody.
The eighth object of this invention is to provide an agent to detect a receptor which recognizes IL-18 using the monoclonal antibody.
The ninth object of this invention is to provide an agent to inhibit IL-18 using the monoclonal antibody.
The tenth object of this invention is to provide a method to inhibit IL-18 using the monoclonal antibody.
The eleventh object of this invention is to provide an agent to neutralize IL-18 using a receptor which recognizes IL-18.
The twelfth object of this invention is to provide a method to neutralize IL-18 using a receptor which recognizes IL-18.
We energetically and extensively screened various means which might attain these objects, eventually resulting in the finding that a substance which recognized IL-18 was present in L428 cell, a type of lymphoblastoid cell derived from a patient with Hodgkin""s disease. We isolated and characterized this substance, revealing that its nature was proteinaceous, as well as that it well recognized and bound IL-18 even when in isolated form. It was also found that the IL-18R protein thus identified was efficacious in treatment and prevention of various diseases resulting from excessive immunoreaction, such as autoimmune diseases, because in mammals including human, the IL-18R protein recognized and neutralized IL-18 which activated immune system. Further, a hybridoma which is producible of a monoclonal antibody specific to the IL-18R protein was established by using as antigen the IL-18R protein, and the produced monoclonal antibody was confirmed to be useful for the purification and detection of the IL-18R protein, and confirmed to efficiently inhibit the physiological functions of IL-18. Thus we accomplished this invention.
More particularly, the first object of this invention is attained by IL-18R protein.
The second object of this invention is attained by an agent which contains as effective ingredient IL-18R protein.
The third object of this invention is attained by a monoclonal antibody specific to IL-18R protein.
The forth object of this invention is attained by a hybridoma which is producible of the monoclonal antibody.
The fifth object of this invention is attained by a process to prepare monoclonal antibody, which comprises the steps of:
culturing in vitro or in vivo a hybridoma which is capable of producing a monoclonal antibody specific to IL-18R protein; and
collecting the monoclonal antibody from the resultant culture or body fluid.
The sixth object of this invention is attained by a method to purify IL-18R protein, which comprises the steps of:
allowing a monoclonal antibody specific to the IL-18R protein to contact with a mixture of the IL-18R protein and contaminants to adsorb the IL-18R protein on the monoclonal antibody; and
desorbing and collecting the IL-18R protein from the monoclonal antibody.
The seventh object of this invention is attained by a method to detect IL-18R protein, which comprises the steps of:
allowing a monoclonal antibody specific to the IL-18R protein to contact with a sample; and
detecting the IL-18R protein through the occurrence of immunoreaction.
The eighth object of this invention is attained by an agent to detect IL-18R protein, which contains a monoclonal antibody specific to the IL-18R protein.
The ninth object of this invention is attained by an agent to inhibit IL-18, which contains as effective ingredient a monoclonal antibody specific to the IL-18R protein.
The tenth object of this invention is attained by a method to inhibit IL-18, which is characterized by allowing a monoclonal antibody specific to the IL-18R protein to act on the IL-18R protein.
The eleventh object of this invention is attained by an agent to neutralize IL-18, which contains as effective ingredient the IL-18R protein.
The twelfth object of this invention is attained by a method to neutralize IL-18, which is characterized by allowing the IL-18R protein to act on IL-18.
L428 cell, which is feasible in this invention, have been deposited in the Patent Microorganism Depository, National Institute of Bioscience and Human-Technology, Agency of Industrial Science and Technology, 1-3, Higashi 1 chome, Tsukuba-shi, Ibaraki-ken, 305, Japan, under the accession number of FERM BP-5777 on and after Dec. 24, 1996.